This application is a 371 of PCT/JP00/00345 filed Jan. 25, 2000.
The present invention relates to a process for producing a glyceryl ether having a low organohalogen compound content.
Glyceryl ethers are generally produced by a process comprising three steps, that is, a first step for reacting an alcohol with an xcex1-epihalohydrin in the presence of an acid catalyst such as sulfuric acid, tin tetrachloride or boron trifluoride-ether complex, thereby obtaining a halohydrin ether; a second step for subjecting the halohydrin ether to intramolecular ring closure by using an alkali, thereby obtaining the corresponding glycidyl ether, and a third step for subjecting the glycidyl ether to hydrolysis or the like treatment. In the first step for addition reaction of the epihalohydrin, however, a 2-mole adduct of the epihalohydrin and an isomer of the halohydrin ether different in alcohol added position are inevitably produced. Since these 2-mole adduct, isomer and the like which are organohalogen compounds cannot be decomposed by the intramolecular ring closure of the second step and even in the third step for converting the glycidyl ether to the corresponding glyceryl ether by a known method (Japanese Patent Application Laid-Open No. SHO 49-86307, SHO 56-133281, HEI 5-32578, or the like), they are hard to be hydrolyzed, the glyceryl ether thus obtained necessarily contains organohalogen compounds.
Such glyceryl ether having a high organohalogen compound content is not suited for use in cosmetics, body detergents and the like which are brought into direct contact with a body upon application.
As means for removing or decomposing such organohalogen compounds, purification or decomposition by a strong alkali can be considered. However, the above-described halohydrin ether different in alcohol added position has physical properties, such as boiling point, close to those of the target glyceryl ether, which makes it difficult to remove it by ordinary purification such as distillation. It is possible to decompose it by adding thereto a strong alkali such as NaOH or KOH, followed by heating, but this means is not preferred, because it causes severe coloration and also a partial decomposition of the target glyceryl ether.
In Japanese Patent Application Laid-Open No. HEI 6-25052, disclosed is a process for reducing an organochlorine content by synthesizing a glyceryl ester and then subjecting it to alkali hydrolysis in the presence of an alcohol. This process which requires a fatty acid in an amount not less than an equivalent mole, however, is by no means economical.
It is an object of the present invention to provide an economical process for producing a glyceryl ether.
It is another object of the invention to provide a process for producing a glyceryl ether which has a markedly low organohalogen compound content.
The present inventors have discovered that the organohalogen compound formed upon preparation of a glycidyl ether can be decomposed by heating the glycidyl ether or a glyceryl ether to a predetermined temperature in the presence of a salt formed from a strongly basic compound and a weakly acidic compound.
The present invention therefore provides a process for producing a glyceryl ether comprising reacting an alcohol with an xcex1-epihalohydrin in the presence of an acid catalyst, subjecting the reaction mixture to ring closure, thereby converting it to the corresponding glycidyl ether and then hydrolyzing the resulting glycidyl ether into the corresponding glyceryl ether, wherein (a) the glycidyl ether is hydrolyzed at 140 to 230xc2x0 C. in the presence of a salt formed from a strongly basic compound and a weakly acidic compound or (b) the reaction mixture after hydrolysis is heated at 100 to 230xc2x0 C. in the presence of a salt formed from a strongly basic. compound and a weakly acidic compound.
The present invention also provides a process for producing a glyceryl ether, comprising:
hydrolyzing a glycidyl ether at 140 to 230xc2x0 C. in the presence of a salt formed from a strongly basic compound and a weakly acidic compound.
The present invention also provides a process for producing a glyceryl ether, comprising:
hydrolyzing a glycidyl ether, followed by
heating the reaction mixture at 100 to 230xc2x0 C. in the presence of a salt formed from a strongly basic compound and a weakly acidic compound.
The present invention also provides a method of reducing the content of organohalogen compound(s) of a glyceryl ether, comprising:
hydrolyzing a glycidyl ether at 140 to 230xc2x0 C. in the presence of a salt formed from a strongly basic compound and a weakly acidic compound.
The present invention also provides a method of reducing the content of organohalogen compound(s) of a glyceryl ether, comprising:
heating a glyceryl ether containing organohalogen compound(s) at 100 to 230xc2x0 C. in the presence of water and a salt formed from a strongly basic compound and a weakly acidic compound.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description.
First, in the present invention, an alcohol and an xcex1-epihalohydrin are reacted in the presence of an acid catalyst, thereby producing a halohydrin ether.
Examples of the alcohol which may be used in the present invention include those represented by the following formula (1):
Rxe2x80x94(OA)pxe2x80x94OHxe2x80x83xe2x80x83(1)
where
R represents a saturated or unsaturated, linear or branched C1-36 hydrocarbon group,
A represents a C2-4 alkylene group, and
p is 0 to 100.
The alcohols where R has 4 to 22 carbon atoms, particularly 4 to 18 carbon atoms, are preferred. Specific examples include saturated aliphatic alcohols such as butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, 2-ethylhexanol and 3,5,5-trimethylhexanol, and unsaturated aliphatic alcohols such as oleyl alcohol and linoleyl alcohol, and alkylene oxide adducts thereof. In the formula (1), A preferably represents ethylene, while p preferably stands for 0 to 20, with 0 being particularly preferred.
Examples of the xcex1-epihalohydrin usable in the present invention include xcex1-epichlorohydrin, xcex1-epibromohydrin and xcex1-epiiodohydrin, of which the xcex1-epichlorohydrin is particularly preferred from the viewpoint of easy availability.
As the acid catalyst, usable in the present invention are, as well as Brxc3x8nsted acids such as hydrochloric acid and sulfuric acid, metal compounds containing at least one element such as boron, aluminum, silicon, titanium, iron, cobalt, zinc, zirconium, tin, antimony or the like which are so-called Lewis acids. Specific examples of the Lewis acid include boron trifluoride-ether complex, boron trifluoride-acetic acid complex, boron trifluoride-phenol complex , aluminum chloride, aluminum bromide, zinc chloride, tin tetrachloride, antimony chloride, titanium tetrachloride, silicon tetrachloride, ferric chloride, ferric bromide, cobalt (II) chloride, cobalt (II) bromide, zirconium chloride, boron oxide and acidic active alumina.
When such a Lewis acid is employed, the reaction can be effected without or after removal of water from the system in a conventional manner, but the latter one is preferred because it brings about an increase in both the reaction rate and yield.
The catalyst is used in an amount of 0.001 to 0.1 mole per mole of the alcohol, with 0.005 to 0.05 mole being particularly preferred.
The formation of a halohydrin ether from an alcohol and an xcex1-epihalohydrin may be conducted in an ordinary manner, described specifically, by reacting, with the alcohol, the xcex1-epihalohydrin which is used in an amount of 0.5 to 1.5 moles, preferably 0.6 to 1.2 moles per mole of the alcohol, in the presence of the above-exemplified acid catalyst at a temperature of 10 to 150xc2x0 C., preferably 70 to 120xc2x0 C. for 0.5 to 10 hours.
From the halohydrin ether obtained by the above-described reaction, the corresponding glycidyl ether and then glyceryl ether may be prepared by removing the catalyst and unreacted raw materials from the reaction mixture if necessary, adding an alkali to the residue, subjecting the resulting mixture to ring closure by dehydrohalogenation and hydrolyzing the dehydrohalogenated product.
Here, ring closure and hydrolysis can be carried out either separately or simultaneously.
When ring closure and hydrolysis are carried out separately, the remaining raw material alcohol and epihalohydrin may be removed by known separating and purifying means such as distillation, washing, recrystallization or column chromatography after completion of the ring closure reaction; or hydrolysis may be effected without removal.
Exemplary alkalis usable in ring closure reaction include hydroxides of an element of Group 1A such as sodium hydroxide and potassium hydroxide and hydroxides of an element of Group 2A such as calcium hydroxide and barium hydroxide. Among them, sodium hydroxide and potassium hydroxide are particularly preferred. The alkali is preferably used in an amount of 1.0 to 4.0 moles, particularly 1.0 to 2.5 moles per mole of the epihalohydrin. The alkali is preferably added, for example, in the form of a 10 to 50% aqueous solution. The reaction is preferably conducted at 40 to 200xc2x0 C. for 0.1 to 20 hours.
The glyceryl ether is available by hydrolyzing the glycidyl ether, which has been obtained in the above-described reaction, by a known manner using an aqueous solution of an acid or alkali.
Examples of the acid or alkali employed for hydrolysis include mineral acids such as hydrochloric acid and sulfuric acid, hydroxides of a Group 1A element of the periodic table such as sodium hydroxide and potassium hydroxide, hydroxides of a Group 2A element such as calcium hydroxide and barium hydroxide, carbonates of a Group 1A element such as sodium carbonate, sodium bicarbonate and potassium carbonate and carbonates of a Group 2A element such as calcium carbonate and magnesium carbonate. Among them, the carbonates of a Group 1A element such as sodium carbonate, sodium bicarbonate and potassium carbonate are preferred from the viewpoint of the selectivity of the reaction.
Water is used in an amount of 1 to 100 mole equivalents per mole of the glycidyl ether, of which the amount of 2 to 10 mole equivalents is particularly preferred from the viewpoint of the selectivity of the reaction and productivity.
The above-described hydrolysis using an acid or alkali can be carried out within a temperature range of 50 to 250xc2x0 C. under normal pressure or under pressure. From the viewpoints of a reaction rate and stability of the compound, the hydrolysis is preferably conducted at 80 to 200xc2x0 C. for 0.1 to 30 hours.
Alternatively, the glycidyl ether can be hydrolyzed, for example, in accordance with the process (Japanese Patent Application Laid-Open No. Hei 5-32578, incorporated herein by reference) using phosphoric acid or activated clay as an acid catalyst and an N,N-substituted amide as a solvent, or the process (Japanese Patent Application Laid-Open No. Hei 7-53431, incorporated herein by reference) wherein the hydrolysis is effected in the presence of a tertiary amine. In the latter process, the hydrolysis is conducted at a temperature not greater than 140xc2x0 C. from the viewpoint of stability. It is also possible to hydrolyze the glycidyl ether through a fatty acid ester, dioxolan or the like.
The present invention is characterized by decomposing the organohalogen compound, which exists with the glycidyl ether, upon or after hydrolysis thereof.
In the case of decomposing the organohalogen compound after hydrolysis, the reaction mixture is heated at 100 to 230xc2x0 C., preferably 130 to 200xc2x0 C., more preferably 150 to 200xc2x0 C. in the presence of a salt formed from a strongly basic compound and a weakly acidic compound, followed by stirring for 0.1 to 100 hours.
Decomposition of the organohalogen compound upon hydrolysis, on the other hand, can be attained by heating the reaction mixture at 140 to 230xc2x0 C., preferably 140 to 200xc2x0 C., more preferably 180 to 200xc2x0 C. in the presence of a salt formed from a strongly basic compound and a weakly acidic compound for 0.1 to 100 hours.
Even in the process (Japanese Patent Application Laid-Open No. Hei 7-53431) wherein the hydrolysis of the glycidyl ether is effected in the presence of a tertiary amine, the organohalogen compound can be decomposed by the reaction at a temperature not less than 140xc2x0 C. The resulting quaternary ammonium salt formed in the system, however, is unstable at a high temperature not less than 140xc2x0 C. and it is decomposed in the system to form a low-molecular-weight amine, which becomes a cause for odor and coloration.
Illustrative of the salt used in the decomposition of the organohalogen compound include salts formed from a weakly acidic compound such as carboxylic acid, phosphoric acid or carbonic acid with a Group 1A element of the periodic table such as sodium or potassium or a Group 2A element such as magnesium or calcium. Among them, salts of a C1-22, particularly C1-18 carboxylic acid and those of carbonic acid are preferred. Specific examples of the weakly acidic compound include saturated or unsaturated C1-22 fatty acids such as acetic acid, propionic acid, butyric acid, octanoic acid,. lauric acid and oleic acid, C2-18 dicarboxylic acids such as succinic acid, adipic acid, glutaric acid and dodecandioic acid, oxycarboxylic acids such as lactic acid, malic acid and citric acid, carbonic acid and acid carbonate. Among them, C2-12 fatty acids and dicarboxylic acids such as acetic acid, octanoic acid, lauric acid and adipic acid are preferred from the viewpoints of reactivity, cost and yield. Particularly preferred are acetic acid and lauric acid.
Accordingly, the compound may be formed from an ion of a metal element from Group 1A or 2A and a weakly acidic compound.
The salt formed from such a strongly basic compound and a weakly acidic compound may be added in the form of a salt or alternatively, the salt may be formed in the reaction system by adding them thereto.
The salt is preferably used in an amount of 0.1 to 50 moles, more preferably 0.5 to 10 moles, particularly 1 to 5 moles per mole of the organohalogen compound contained in the glycidyl ether. Here, the amount of the compound of the organohalogen compound contained in the glycidyl ether is determined by gas chromatography.
The glyceryl ether thus obtained can be isolated and purified by known isolating and purifying procedures, such as, for example, distillation, washing, recrystallization, column chromatography, or the like.